Check if parameters are equal in jjt

Author: dlfivefifty

src/cjt.jl

@@ -140,7 +140,14 @@ given the Jacobi expansion coefficients ``c`` with parameters ``α`` and ``β``.
 
 See also [`cjt`](#method__cjt.1) and [`icjt`](#method__icjt.1).
 """
-jjt(c,α,β,γ,δ) = icjt(cjt(c,α,β),γ,δ)
+function jjt(c,α,β,γ,δ)
+    if isapprox(α,γ) && isapprox(β,δ)
+        copy(c)
+    else
+        icjt(cjt(c,α,β),γ,δ)
+    end
+end
+
 
 """
 Pre-plan optimized DCT-I and DST-I plans and pre-allocate the necessary

test/runtests.jl

@@ -88,6 +88,12 @@ pop!(c)
 c = [1.0;2.0]
 @test norm(jjt(c,0.12,0.34,0.12,0.34)-c,Inf) ≤ 2eps()
 
+
+# test same parameters
+
+c=[0.,1.]
+@test jjt(c,1.5,-0.5,1.5,-0.5) == c
+
 println("Testing the special cases (α,β) = (±0.5,±0.5)")
 
 # Chebyshev coefficients of exp